1. Field of the Invention
The present invention relates to a switch module that generates an operation signal when the switch module is activated, and more specifically to a switch module that illuminates an operation portion or operation buttons of a keypad, a numerical keypad, an operation keyboard or the like in electronic devices such as mobile phones, mobile information terminals or the like.
2. Description of the Related Art
There is conventionally known a switch module, which is disclosed in FIG. 6 of the Japanese Patent Application Publication No. 2004-69751, for example. The switch module includes a substrate 63, a plurality of fixed contacts 62 provided on the substrate, a movable switch 64 comprising a tact spring disposed to cover each of the fixed contacts, a light-guiding sheet 21 disposed above the tact springs, and light sources 26 disposed to face an end of the light-guiding sheet 21. The switch module includes a plurality of key tops 65 each having a character printed thereon and is provided above the light-guiding sheet 21. In the switch module, each key top can easily be discriminated by illuminating light emitted from the light-guiding sheet to a character printed on each key top.
There is also known a switch module 1 including a detection panel 2 which is disposed upwardly and has a plurality of input areas T1 to T4, a display sheet 3 which is disposed under the detection panel 2 and has displays S1 to S5, and a light-guiding sheet 5A disposed under the display sheet 3 (for reference, see Japanese Patent Application Publication No. 2004-227997 (FIG. 2)). In the switch module, the detection panel 2, the display sheet 3 and the light-guiding sheet 5A are stacked, and each of the displays is discriminated by illuminating the display sheet 3 by the light-guiding sheet 5A.
However, in the aforementioned conventional switch module where the characters printed on the key top are lighted, there is a structure in which a plurality of characters or numbers for which switching character input modes is necessary are displayed on one key. In this case, there is a problem that it is not possible to determine which display corresponds to an operated key by only viewing the key top.
On the other hand, in the aforementioned conventional switch module in which the detection panel is placed on the display sheet, even if the input areas can be discriminated, it is not possible to obtain a good handling feeling when operating the display sheet because the detection panel is placed upon the display sheet, although the inputting areas can be clearly recognized.